One of the most significant challenges when processing semiconductors is the ability to accurately measure the temperature of substrates during the heating process. In the past, various means and devices for measuring the temperature of substrates in thermal processing chambers have been developed. Such devices include, for instance, pyrometers and thermocouples that directly contact the substrate or that are placed adjacent to the substrate. Non-contact measurements also can be used to probe the optical properties of the substrate in order to determine temperature.
In some techniques, such as some reflectance- and transmittance-based measurements, for example, the resulting temperature measurement will be the result of the variation of the optical absorption coefficient of silicon with temperature. Different approaches have been proposed for temperature measurements with regard to determining temperature in ranges below about 800° C., but known techniques cannot be relied upon to always provide optimal, or even useful, measurements above about 800° C.